But the bill is probably doomed. Leaders of the Senate Republican caucus have demanded votes on unrelated amendments, which Reid declined. Reid instead offered Republicans a chance to vote on a separate bill that would force the approval of the Keystone XL pipeline — but only if they first approve the energy efficiency bill.

Reid on Wednesday rejected McConnell’s amendment request and filed for a cloture vote to end debate on the energy efficiency bill, which would be subject to a 60-vote threshold. Because of the fighting over the amendment issue, the bill seems unlikely to clear that threshold when it comes up for a vote, which is expected on Monday.

This isn’t the first time that the energy efficiency bill, from New Hampshire Democrat Jeanne Shaheen and Ohio Republican Rob Portman, has been dashed. The two senators first introduced energy efficiency legislation in July 2011. They offered it again in April 2013, and their bill passed the Energy Committee a year ago.

It went up for a debate on the Senate floor in September, but Republicans tried to attach a measure to delay the implementation of Obamacare. Shaheen and Portman revised the bill and reintroduced it earlier this year.

The bill is about as non-controversial as you get in Washington. It includes incentives, opportunities, and funding to improve energy efficiency in commercial buildings, houses, and appliances, but no mandatory standards. Still, the American Council for an Energy-Efficient Economy has estimated it will spur the creation of 190,000 jobs, save the country $ 16.2 billion a year on energy bills by 2030, and reduce planet-warming greenhouse gases. And the American Chemistry Council, the American Gas Association, and the Earth Day Network all signed a letter supporting it last month.

Still, the legislation appears headed for demise.

“We have been through this a number of times … but Shaheen and Portman did not give up,” Reid said. He added that the bill’s sponsors had already incorporated 10 bipartisan amendments before reintroducing the measure this year, but McConnell now insists that Republicans be allowed to offer five additional amendments, including one for the Keystone pipeline. “It’s been very, very difficult to pin down the Republicans for anything more than a day or two, because they keep changing their minds,” Reid said Wednesday.

Republicans said they just want to use this as an opportunity to discuss other energy-related measures. “The majority leader has refused for seven years to allow a serious debate on energy in this chamber,” McConnell said, adding that Republicans were concerned with establishing a greater U.S. energy presence overseas and stopping the Obama administration’s “elitist war on coal.”

“That’s why we planned to offer forward-leaning amendments that aim not just to increase energy security, but to also improve national security and economic security for the middle class,” McConnell said.

In addition to attaching the approval of the controversial Keystone XL pipeline to the bill, Republicans sought a vote on amendments that ranged from expediting the export of American energy, to preventing the Obama administration from moving forward with new regulations on coal-fired power plants. Attaching any of those to the bill would be a poison pill for many supporters — and most likely for President Barack Obama.

The bill’s fans in the environmental community accused McConnell of using the legislation to grandstand on other issues.

“Minority Leader Mitch McConnell is choosing to play 2014 politics instead of allowing a bipartisan bill to go forward,” said Franz Matzner, associate director of government affairs at the Natural Resources Defense Council. “It’s the definition of political hostage-taking. It’s a bill that would easily pass.”

The Senate, said Sierra Club deputy legislative director Melinda Pierce, has become the place where “even the most modest of proposals with bipartisan support goes to die.”

“The Republicans are not willing to let anything pass without doing health care, without taking a swipe at Keystone, without trying to block EPA carbon regulations,” said Pierce. “I think we’re going to face it again and a gain on any piece of legislation.”

Elizabeth Tate, director of government relations at the Alliance to Save Energy, said her group is still “very optimistic” that the impasse can be resolved. “We really urge the lawmakers to set aside election year politics and to move something forward that would really benefit Americans,” said Tate. “It’s sad that such a good bill gets mired down in other politics.”